STFT Trims off?

Watermelon

Lurker
Mar 13, 2018
17
8
0
Ride
535i FBO+
Trying to figure out why my STFT is so far off. I have flashed my car back to Stage 0 map from Cobb. These are my fuel trims for STFT LTFT HPFP LPFP, something seems off to me and i cannot figure out why, i have replaced all spark plugs gaped at .020" (NGK 95770) and i have replaced injectors 1,2,3,6 with new index 12 injectors. injectors 4,5 are index 12 but have about 20-30k on them. I originally thought the STFT was so far off because of a bad tuning map done on the dyno from the previous owners time with the car. But now im beginning to think this is a hardware issue not software. I looked in each cylinder with a borescope for injector leakage. I unplugged all the injectors and turned the motor over and saw no leakage in the cylinders. I also ran a leak down test and saw only 3.5-8% leakage in the cylinders. What could be causing the difference in STFT bank 1 & 2? here are the maps from the stage 0 map holding at 2500 rpm and just at idle.

https://datazap.me/u/watermelon13/log-1521829947?log=1&data=2-15-16
 

veer90

Lieutenant
Nov 16, 2016
1,000
764
0
West Nyack, NY
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e90 335i 6MT
Go for a drive and see what they look like then. Oscillating STFT while driving under light throttle input is a one or multiple bad injectors or bad O2s. Oscillation under no load really doesn't mean anything.

Trying to zero out STFTs is a wild goose chase. You just want to make sure they aren't pegged at +34% or -34%. Some bank to bank variation is also normal depending on your injectors and fuel scalars.
 

Watermelon

Lurker
Mar 13, 2018
17
8
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535i FBO+

R.G.

Lieutenant
Nov 17, 2016
669
325
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Henderson, NV
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E92 335, F10 M5
Could be the downpipe to turbo gasket pre O2 is worn out but they’re pretty stout. Unless someone forgot to put back after a pipe swap?

Agree with Veer on a general basis. You might be on a wild goose chase. I’d do a full INPA reset of lambda adaptations, then let it idle in P for 10 min and see if they balance themselves out


Can’t see the chart for sht on my phone, what’s the % discrepancy?
 

Watermelon

Lurker
Mar 13, 2018
17
8
0
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535i FBO+
I put the downpipes on when I rebuilt bank 2 turbo. What’s the pre cat 02 gasket you’re talking about. Both 02 came out. But I never saw a gasket laying on the ground during mop up
 

Watermelon

Lurker
Mar 13, 2018
17
8
0
Ride
535i FBO+
I’ve got variances all over the place. With the customtune I’m seeing bank 2 at almost 28-30 at some places and bank 1 usually won’t go higher than 18. But with the stage 0 map I’m seeing lower overall numbers. But a decently wide variance between the two. Maybe 10-12% variance
 

Watermelon

Lurker
Mar 13, 2018
17
8
0
Ride
535i FBO+
Yeah i replaced both of those with BMW ones when i rebuilt the turbo, they have maybe a few hundred miles on them. That doesnt mean that i didnt mess them up when i was fighting to install the downpipes all night.

heres a log with Cobb Stage 2+ FMIC Aggressive tune on my car
https://datazap.me/u/watermelon13/log-1521912458?log=0&data=2-21
there is a full pull in 4th gear and a pull in 3rd gear as well. LTFT looks better, STFT still looks the same while the Lambda is almost spot on for both banks... is it just that injector 4&5 are older and need more fuel to keep up with the new injectors on bank 1?
 

R.G.

Lieutenant
Nov 17, 2016
669
325
0
Henderson, NV
Ride
E92 335, F10 M5
Ok, looked at this log. Honestly nothing that serious. AFR's are on point. Gaskets are fine if you remember swapping them, don't waste your time. They stick to the grooves really well, doubt one came loose when dealing with v band hell.


If it's really bothering you:
How many miles since you flashed the tune and what index are the injectors? How many miles on 02's? 02 sensors reliability goes down with age.

If injectors are fairly new, than likely it's simply either adaptations and if your running Cobb with no INPA access just re flash map and putz around for 50 miles so they try to re calibrate or it's something a fresh pair of 02's can solve.

Get some techron injector cleaner additive (don't roll eyes mofos, it helps with small shit like this), re flash and then take another look.
 

Watermelon

Lurker
Mar 13, 2018
17
8
0
Ride
535i FBO+
All injectors are brand new index 12 except cyl 4&5. They have 30k on them. I’m not sure if o2 has ever been replaced, car has 182k on it now.
Problem I am having is a misfire on 4&5 during cold start. You can hear it go away after the cold start is over. And a cyl 6 misfire under wot at redline in 3rd gear. But only if you start at around 5k rpm. If you do a pull from 2500 to redline it doesn’t triplgger a SES light
 

R.G.

Lieutenant
Nov 17, 2016
669
325
0
Henderson, NV
Ride
E92 335, F10 M5
All injectors are brand new index 12 except cyl 4&5. They have 30k on them. I’m not sure if o2 has ever been replaced, car has 182k on it now.
Problem I am having is a misfire on 4&5 during cold start. You can hear it go away after the cold start is over. And a cyl 6 misfire under wot at redline in 3rd gear. But only if you start at around 5k rpm. If you do a pull from 2500 to redline it doesn’t triplgger a SES light

Could be the plugs as my car never ran well with NGK's for whatever reason. Tighten gap a bit is something you can try. 02s if original should have been replaced regardless as they won't be near as accurate as they should even with 100k on them. Ambient temps and fuel type also play a factor in cold start issues. A lot of little variables could be at work. Try removing the easier variables like plug gaps first would be my suggestion for cold start stumbling.
 

Beemin

Private
Nov 5, 2016
41
7
0
Los Angeles
Trying to figure out why my STFT is so far off. I have flashed my car back to Stage 0 map from Cobb. These are my fuel trims for STFT LTFT HPFP LPFP, something seems off to me and i cannot figure out why, i have replaced all spark plugs gaped at .020" (NGK 95770) and i have replaced injectors 1,2,3,6 with new index 12 injectors. injectors 4,5 are index 12 but have about 20-30k on them. I originally thought the STFT was so far off because of a bad tuning map done on the dyno from the previous owners time with the car. But now im beginning to think this is a hardware issue not software. I looked in each cylinder with a borescope for injector leakage. I unplugged all the injectors and turned the motor over and saw no leakage in the cylinders. I also ran a leak down test and saw only 3.5-8% leakage in the cylinders. What could be causing the difference in STFT bank 1 & 2? here are the maps from the stage 0 map holding at 2500 rpm and just at idle.

https://datazap.me/u/watermelon13/log-1521829947?log=1&data=2-15-16

Any luck figuring this out? I’m having a similiar issue.
 

Beemin

Private
Nov 5, 2016
41
7
0
Los Angeles
What are your STFT and LTFT at hot idle? A good 30 second log will do.

Not OP but my situation is similar so hopefully my experience will contribute to a solution.

My stft at idle aren’t consistent. They typically range from -2 to +2 with a small 1-2% variance between banks.

My Ltft are at 10.9 and 4.7 during idle at the moment.
 

BQTuning

Corporal
Jul 18, 2017
174
139
0
www.bqtuning.com
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E89 Z4 35i 6MT M Sport
Relocated inlets here. Why?

Based on my personal experience with my own car. Switch the DCI around and see if trims activity reverse on the banks. I have seen on my own car if there is significant airflow difference between both banks it has an impact on fuel trims. It could be one of the filters is clogged up with more dirt etc....
 

Beemin

Private
Nov 5, 2016
41
7
0
Los Angeles
Based on my personal experience with my own car. Switch the DCI around and see if trims activity reverse on the banks. I have seen on my own car if there is significant airflow difference between both banks it has an impact on fuel trims. It could be one of the filters is clogged up with more dirt etc....

I recently swapped in some brand new filters as maintenance unrelated (or so I thought) to my trim issue. Didn't seem to affect the logs. I appreciate the input though.